Tennis is ready for a change, and this week can be a good opportunity for that. Nadal is out with a knee injury, the hard courts take away the advantages that Federer and Murray have on grass, and Djokovic has not played to his ability in the past few months.

If everything breaks right, one of these men can shock the world and be the next U.S. Open champion.

Milos Raonic

Few players in the world have been climbing faster in the rankings than Milos Raonic. The 21-year-old is now up to No. 16 in the rankings after defeating Tomas Berdych last week, which is the highest mark ever achieved by a Canadian.

His serve will continue to take him higher. He is a close second in total aces this year behind John Isner and leads in first serves won. This has helped him win a world-leading 93 percent of his service games.

He needs to improve his return game, but his consistency with the serve will make him a tough out for any opponent.

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Juan Martin del Potro

The Argentine has the distinct honor of being the only player outside of the "Big Three" to win a Grand Slam title since 2005. In 2009, del Potro upset Roger Federer in the finals of the U.S. Open to take home the crown as a 21-year-old.

Unfortunately, a wrist injury has slowed his career and prevented him from taking the next step.

Del Potro is finally returning to form this year, winning two tournaments and earning the bronze medal in the Olympics. He narrowly lost to Federer in the semifinals of the London Games and should be able to keep that momentum heading into the U.S. Open.

John Isner

Although he is possibly the best server in the world, John Isner has not been able to turn that into success in the major tournaments.

He has only won three career titles, and only once has he reached the quarterfinals of a Grand Slam event.

Still, the No. 10 player in the world is someone that no one wants to face in the U.S. Open. He already serves hard, and the American will have the home crowd behind him to add a couple of miles per hour with adrenaline.

Isner leads the tour with 756 aces in only 51 matches and gets his first serve in play 68 percent of the time. If he gets a good draw where he does not have to face a top server, he can have a deep run in this prestigious tournament.